Problem:
Grey imported HJ61 Landcruisers have a 24 volt electrical system, yet all my toys run off 12 volts. There are two batteries connected in series, using both battery bays alongside the radiator. The alternator also only puts out 35 amps which is low if you’re running extra batteries.
In this article, I will run through the various options and solutions I have encountered in my journey to where I am now. I’ve also learnt a neat trick to really beef up the output of these alternators.
I’m posting this trying to be helpful to others in the same situation as me, not to start a technical discussion on the merits of what I have done. I'm not a sparky or technically qualified, I'm a Social Worker that likes fiddling with stuff.
………
The truck.
HJ61 with a 12HT with 90,000kms on the clock when I bought it eight months ago as a try out for getting into 4WDs. Full electics, PTO winch, sun roof - very very neat inside and mistaken as new by people who didn't know their models.
There are a number of problems associated with a 24 volt setup, plus some advantages. The biggest advantage is how quickly the motor turns over and starts. Any 24v equipment uses less amps than it’s 12 volt copy and generally is more electrically efficient. Cabling does not need to be as thick due to the decreased amps.
The disadvantages are:
• How to run 12-volt appliances.
• How to effectively recharge after running high load 12-volt appliances.
• Where to place an auxiliary battery as both battery bays are already used.
• How to power trailer lighting.
You can get 12 volts out of this system by connecting a wire to the negative pole of the high battery, but if you run more than a low current radio etc., the alternator cannot tell that one battery is discharged more than the other and it will eventually overcharge one battery, reducing it’s life.
One solution is to buy a 24v to 12v converter. This is an easy solution, but you need to buy a unit to cater for your current draw and they are not all that cheap. You also lose efficiency through the converter. This was the initial solution I installed until the converter stopped working. I think I overloaded it.
Another solution is to install a second alternator below the first on the passenger side of the motor or wherever you can fit it. This requires an auxiliary battery to be permanently installed so the alternator can charge it, and fiddling around with belts, brackets etc., but is not a bad solution. High capacity alternators are cheap to buy from a wrecker and if you do the work yourself building brackets it would be the cheapest solution. Doing this and finding a permanent home for an auxiliary battery would be the greatest hurdles I imagine.
The solution I have ended up with involves two Redarc products, a multiple relay gizmo I built for the trailer lights and a battery isolator kit from Dick Smith.
I pull all my 12v current from the centre tap on the batteries. All the main current carrying cables are 50 amp 7.1mm² distributed via 3 fuse boxes in various regions of the vehicle. This cable also runs the full length of the vehicle inside some garden hose inside the chassis rails. Voltage drop is minimal anywhere. All joints are soldered. The auxiliary battery is in a battery box in the rear cargo area of the Landcruiser and connected into the system on an as needs basis by a 32v plug.
The main start batteries are recharged equally through a Redarc CE20 Charge Equaliser that balances the two batteries. They are protected from over discharge by a Redarc Smart Start battery isolator that disconnects the 12-volt supply at 12.2 volts. Redarc modified the standard setting of 12.6v on request. It does not protect them from discharging via the 24-volt circuit such as leaving headlights running.
The auxiliary battery is protected from overdischarge by a Battery Isolator kit from Dick Smith set to cut out at 11.4 volts.
I made a unit from several 24v 5-amp relays to run the trailer lights. The 24v lighting circuits switch on the relays, and power for the trailer plug comes from the 12-volt circuit. Hella make these units to buy off the shelf. Altronics supply suitable relays on a strip.
There is a switch on the dash to override the Redarc isolator so I can choose to pull more capacity from the main start batteries, and also one to override the 12 volt supply from being normally controlled by the Accessories switch on ignition. This is helpful when I want to take the keys out of the ignition and leave a fridge running for example.
In this scenario, the Redarc Isolator will protect the main batteries. If I have the auxiliary battery fitted, the fridge will still run after the main start batteries have been turned off by the isolator and the fridge will be powered by the auxiliary until that drops it’s capacity when the Dick Smith kit kicks in and turns it off.
Yet to be finalised is a Dick Smith voltage meter connected by a rotary switch to each of the batteries so I can keep a check on the voltage in each battery.
I’ve also had problems with the alternator on this vehicle not producing enough amps to cope with the accessories. Drive In Electrics in Wangara have fitted a 12 volt 60 amp stator to the 24-volt alternator so now I have 60 amps at 24 volts – plenty of grunt. As far as I know, the stator was from a 12 volt Landcruiser alternator of the same model. An additional problem was the voltage regulator limiting charge to 25.5 volts – way too low. A tweak on the tab inside the regulator has bought charge up to 28.8 volts and an extra 50-amp cable running direct from the alternator to the battery has resolved a voltage drop problem.
If it sounds complex, it is. I am running a 24-volt and a 12-volt electrical system. It’s been a bit of a head spin at times, but I ‘think’ I’m over
the hump now.
I trust this is useful.
Thanks
Tim